package com.jly.sqlSession;

import com.jly.config.BoundSql;
import com.jly.pojo.Configuration;
import com.jly.pojo.MapperStatement;
import com.jly.utils.GenericTokenParser;
import com.jly.utils.ParameterMapping;
import com.jly.utils.ParameterMappingTokenHandler;


import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {

    //params user参数
    @Override
    public <E> List<E> query(Configuration configuration, MapperStatement mapperStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, IntrospectionException, InstantiationException, InvocationTargetException {
        //1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //2获取sql语句  select * from tb_user where id = #{id} and username = #{username}
        //转换sql语句   elect * from tb_user where id = ? and username = ?,转换过程中还要对#{}立面的值进行存储
        String sql = mapperStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象,prepareStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4.设置参数
        //获取参数的全路径
        String paramterType = mapperStatement.getParamterType();
        Class<?>  paramterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
              //获取当前的储值对象
            Field declaredField = paramterTypeClass.getDeclaredField(content);
              //设置暴力访问
            declaredField.setAccessible(true);
              //就是获取的参数值
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);

        }
        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mapperStatement.getResultType();
        Class<?> classResultType = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();
        //6.封装返回结果集
        while (resultSet.next()){
            //获取元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            Object ob = classResultType.newInstance();
            for (int i = 1; i <= metaData.getColumnCount() ; i++) {
                //得到列字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的关系，完成封装
                //classResultType 和 columnName 生成读写方法
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, classResultType);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(ob,value);
            }
            objects.add(ob);
        }
        return (List<E>) objects;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;

    }

    /**
     * 完成对#{}的解析工作：1.将#{}用？代替，2.解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {

        //标记处理类：配置标记解析器来完成占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();

        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析过后sql
        String parseSql = genericTokenParser.parse(sql);
        //#{} 立面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);

        return boundSql;


    }
}
